This invention relates to culture medium containers for analysis of bacteria.
Air bacteria analysis according to the impaction method, in which commercially available petri dishes are used, represents one of the most commonly applied methods. In all applications known so far, the culture medium tub of the petri dish is introduced into a specially constructed suction chamber of the air suction unit. This suction chamber has suction apertures (holes or respectively slits), through which the environmental air is suctioned. As a result of the volume of the airstream and the geometry of the suction apertures, the particles in the airstream are accelerated so much that the air particles strike the underlying surface of the culture medium in the culture medium tub, and are received there.
This method has a system-dependent course, is very time-consuming, and handling is complicated. The petri dish first has to be opened. During the measuring period, the lid must be kept in such a way that no sterilization error occurs. The culture medium tub of the petri dish must be inserted without sterilization errors into the suction chamber of the device. After measurement, the whole thing takes place in reversed order.
Owing to the different filling levels of the culture medium (depending upon the manufacturer), the spacing between the culture medium surface and the air admission plane, of the suction chamber, must be corrected. If this is not done, a measuring mistake can occur.
The invention presented here has as its object overcoming all these drawbacks.
The invention has, as subject matter, a culture medium container, which is useful for air bacteria analysis in particular according to the impaction method. The culture medium container comprises a dish and a fitted lid, and includes an integrated geometry for air suction and air conduction in the form of apertures in lid and dish.
The culture medium container according to the invention, which is intended for air bacteria analysis according to the impaction method, represents a further development of the petri dish.
The culture medium container comprises a dish or tub and a lid. The two parts are made preferably of injection-molded plastic, e.g., polycarbonate. The dish or tub can be provided with culture medium by the manufacturer or by the user.
The lid is provided with air suction apertures, holes or slits, which have preferably an optimized suction geometry. In one embodiment, a tapered recess is located in the middle of the lid for the purpose of mechanical connection to the dish.
The dish has in the middle a protuberance directed into the dish interior, which protuberance is provided with at least one or more apertures for air outlet. The edge of the protuberance represents a hole directed downward, into which the said apertures come out. The hole has preferably a conical shape, for receiving an air suction device or air suction hose. There is, if necessary, for mechanical connection to the tapered recess of the lid a tapered area in the upper region of the protuberance.
The culture medium containers are normally supplied filled in a sterile way and stacked. For measurement purposes, a container can easily be withdrawn and put directly on an air suction unit or over the hose connection. Afterwards, the measurement takes place in that a defined volume of air, e.g., from 501 up to 10001, is suctioned in for a certain period of time. The direction of flow of the air is indicated by means of arrows in FIG. 1, FIG. 3 and FIG. 4. After the measurement, the container is removed, stacked in a transportable way, and then incubated. Not until after incubation is the container lid removed for the bacteriological analysis.
In addition to the definition of the invention according to claim 1, special embodiments of the culture medium containers for air bacteria analysis according to the present invention can have the features mentioned in the following, either alone or in a desired combination:
A system-dependent impaction distance within very narrow tolerances (FIGS. 1, 2) between the air admission plane and the culture medium surface.
A mechanically stable connection between the lid and the tub by means of conical plug-in connection.
An airtight and hermetic connection between the lid and the tub, if necessary the sealing being achieved by means of O-ring.
The lid is provided with air suction apertures.
The air suction apertures have an optimized suction geometry.
The air suction apertures can have different aperture sizes.
Different lids with varying aperture sizes should be available so that a differentiation according to particle size is possible.
Adaptation of the culture medium containers for a cascade-like configuration of a plurality of culture medium containers. For this purpose a cascade connecting hood is proposed, which makes possible, by means of O-ring, a hermetic serial configuration of, for example, three culture medium containers over one another, each with a lid of different suction aperture size. This allows a differentiation according to particle size.
All system parts have a mechanical, stable, conical plug-in connection to one another.
The culture medium container lid is provided with a central recess which makes possible a stable conical connection to the dish or to the culture medium tub.
The culture medium dish is preferably provided with a central protuberance, which has on its upper side and on its lower side one connecting socket each, each with a blind hole. The blind hole of the upper connecting socket serves to receive the recess of the lid for the purpose of stable conical connection of the culture medium container lids, while the blind hole in the lower connecting socket optionally serves to receive a connecting peg.
The central protuberance of the culture medium dish has air passages.
The geometry of the recess in the lid and the geometry of the protuberance in the dish allow a plug-in connection by means of the above-mentioned connecting peg for the purpose of stacking a plurality of culture medium containers without cascade hood.
The dimension of the connecting peg can be selected in such a way that, when stacking, an air gap remains between the dish and the lid for the purpose of air exchange during incubation.
The length of the connecting peg can also be selected in such a way that the lid of the dish and the bottom of an adjacent dish are in mutual contact without any gap so that no air exchange is possible.
The protuberance of the dish allows a mechanically stable conical connection to air suction hoses, air suction units, cascade connecting hood, and to the sealing peg.
By means of a simple plug-in connection, the culture medium container can be placed on an air suction-in unit or respectively on an air suction-exhaust unit.
The present invention will be explained more closely by means of the attached FIGS. 1 to 5.